The Australian and US researchers used global positioning system (GPS) equipment and seismometers for the first time to measure the behaviour of rifts in the Amery ice shelf, including a set of fractures known as the Loose Tooth.

The study found that fracturing is variable and spasmodic, much like earthquake activity, Young says.

The team found three episodes over 35 days and noted bursts where a rift lengthened by almost 200 metres over four hours.

"If you don't look frequently enough then what you see is apparently a slow steady rupturing whereas if we look in detail we find it's not like that at all," Young says.

Climate change threats

The researchers also found that rifts grow faster in summer than in winter, challenging assumptions that dynamic forces, not climate change, cause ice shelves to break up.

"In broad terms there appeared to be little activity, almost none, in the winter months and most of the activity in the summer months," Young says.

"We've now seen that [the ice shelf] is very sensitive to changes that are represented by seasonal change, so it could be quite sensitive to small changes in climate, either ocean or atmosphere."

A disintegration of the ice shelves, which are a floating extension of continental ice sheets, could have a major impact on sea levels, Young says.

This is because they moderate the flow of continental ice into the sea.

Waiting for the Antarctic tooth fairy

Loose Tooth is opening up at between 2 and 5 metres a day along a 15 kilometre front, says Australian scientist Dr Richard Coleman of the University of Tasmania and the ACE CRC, who was also involved in the research.

He says the rifts have been widening steadily for five years.

"If it keeps tearing through at that rate we suspect that a 30 by 35 kilometre chunk will come out in the next couple of years," he says.

"Over time it will have an input of fresh water into the ocean area which will change the ecology."